package day06;

import java.io.IOException;

public class P06BasicIO {
    //EOF =End of File  -1
    static int readInt() throws IOException{
        int s=0;
        int x;
        while((x=System.in.read())!=-1){
            if(!Character.isDigit(x))
                break;
            s=s*10+(x-'0');
        }
        return s;
    }

    public static void main(String[] args) {

        //read write  //低级IO
//       try{
//           int x=System.in.read();
//           System.out.println(x);
//       }catch (IOException e){
//           e.printStackTrace();//异常默认的处理，输出异常触发的栈
//       }
        try{
            int x=readInt();
            System.out.println(x+x);

        }catch (IOException e){

        }



    }
}
